The present invention relates to a magnetic scale for use in position detection.
A position detecting device for detecting the position of a print head in a printer is proposed in Japanese Patent Laid-open No. Sho 62-226007, for example.
This position detecting device includes a magnetic scale and a magnetic sensor. The magnetic scale is provided with magnetic marks formed on the outer circumferential surface of a guide shaft for axially guiding the print head and arranged in the longitudinal direction of the guide shaft. The magnetic sensor is integrated with the print head and detects a change in magnetic field of the magnetic marks, thereby outputting a detection signal.
Then, the position of the print head in the longitudinal direction of the guide shaft is obtained according to the detection signal output from the magnetic sensor.
Such a position detecting device having a magnetic scale is widely applied to various machine tools, printers, automatic machines, etc. requiring position detection.
In the above-mentioned position detecting device, a magnetic member of the magnetic scale is exposed to the outside of the device. Accordingly, in the case that the position detecting device is mounted on a machine tool or the like, there is a possibility that an object may strike the magnetic member to damage it or a cutting fluid may adhere to the magnetic member to degrade it, causing a disadvantage in ensuring the durability of the magnetic scale.
It is accordingly desirable to provide a magnetic scale which can reliably protect a magnetic member included therein to improve its durability.